Regulating-controller for electric motors.



H. R. STUART.

REGULATING CONTROLLER FOR ELECTRIC MOTORS.

APPLICATION FILED JULY 17. 1912.

1 231 66; Patented July 3, 191?.

14% BY I A'TTORNEY UNITED STATES PATENT OFFICE.

R. STUART. OF SPRINGFIELD, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC ANDMANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

REGULATING-CONTROLLER FOR ELECTRIC MOTORS.

Specification of Letters Patent.

Patented July 3, 1917.

Application filed July 17, 1912. Serial No. 710,032.

To (ZZZ whom it may concern Be it known that I, HARVE R. STUART, acitizen of the United States, and a resident of Springfield, in thecounty of Clark and State of Ohio, have invented a new and usefulImprovement in Regldating-Controllers for Electric Motors, of which thefollowing is a specification.

My invention relates to the regulation and control of electric motorsand it has special reference to such systems as embody automatic meansfor governing the secondary resistances of polyphase induction motors.

The object of my invent-ion is to provide simple and automatic means,that shall respond promptly to small variations in the load and in thespeed of a polyphase induction motor, and so adjust its secondaryresistance, as to hold the motor at a substantially constant speed undervarying loads.

The single figure 0]": the accompanying drawings is a diagrammatic viewof a system of regulation and distribution embodying my invention.

Referring to the drawing, the primary winding 1 of an induction motor 2is supplied with energy from any suitable polyphase source, throughconductors 3, el and 5.

The motor secondary is provided with collector rings 6, 7 and 8 andcooperating brushes 9, 10 and 11, through which a connection isestablished to external resistance sections 12, 13 and 14.

Each of the resistance sections is provided with a. plurality ofintermediate taps which are respectively connected to a series ofstationary contact members 15. These contact members are arranged inthree groups and are disposed substantially in the arc of a circle.

A rotatable contact member 15 having three arms 16, 17 and 18, isadapted to sweep over the stationary contact members and to ismechanically connected to the induction motor 1 and is electricallyconnected across the terminals of a constant potential direct currentsource 24, the armature 20 of the motor 19 being included in seriescircuit relation with the generator armature 2:2.

The generator 21 is so connected to the tor depends, of course, upon themotor load.

The generator is designed to produce an electromotive force which 18substantially equal and opposite to, and therefore neutraiizes, theelectromotive force of the constant potential source 24 when the motorspeed is normal. Consequently, under these conditions, the motor 19 willbe at rest and no adjustment of the rotatable contact member 15 will beeffected.

The operation of the system is it follows:

Assuming that the load on the motor is light and that the rotatablecontact member 15 occupies the position shown in the drawing, if themotor load is increased, the speed will diminish somewhat and the motor19 will be so operated, by reason of the resulting preponderance of theconstant-potential source, as to rotate the contact member 15 and itsarms 16, 17 and 18, in a counterclockwise direction and thus exclude acorresponding portion of each of the resistance sections 12, 13 and 1 1from the secondary winding circuit of the motor. The motor speed willaccordingly increase and restore the balanced relation between thegenerator electromotive force and the electromotive force of theconstant potential source 24.

The rotatable contact member will be at rest until there is anotherchange in the load of the motor.

From the foregoing, it is evident that the speed of the induction motoris automatically maintained substantially constant, irrespective of loadvariations.

While I have shown a three-phase induction motor, my invention is notrestricted to this arrangement and I desire that only such limitationsshall be imposed as are indicated in the appended claims.

I claim as my invention:

1. An induction motor having a speedgovernor comprising a resistor,means for including variable amounts of the resistor in the secondarycircuit of the motor and a controlling means comprising two opposingelectromotive force generators one of which is driven by said motor andthe other of which has a substantially constant voltage value.

2. An induction motor having an adjustable secondary resistance, agenerator operatively connected to the motor, an opposing source ofenergy connected to the terminals of the generator and normallyneutralizing the generated electroinotive force, and means dependingupon a ditl'erence between the electromotive forces of the generator andof said source for automatically adjusting the secondary resistance ofthe motor.

An induction motor having an adjustable secondary resistance, agenerator operatively connected to the motor, an opposing source ofenergy connected to the terminals of the generator and normallyneutralizing the generated electromotiveforce, and electro-res 'ionsivemeans, depending upon a'difference between the electromotive forces ofthe generator and of said source, for automatically adjusting thesecondary resistance ofthe motor.

4. A polyphase induction motor having an adjustable external resistance,stationaryand movable contact members for determining the active portionof the resistance, a small motor operatively connected to the movablecontact member, and a pair of op posed sources of energy normallyneutralizing each other and tending to act upon the motor, oneof saidsources being operatively dependent upon the induction motor.

A polyphase induction motor having an external secondary resistance, acontroller for adjusting the resistance, a pilot motor operatiyelyconnected to the controller, a generator operatively connected to theinduction motor, a constant -po'tential source of energy connected tothe terminals of the generator and normally neutralizing the generatedpotential, said pilot mot-orf being interposed between theconstant-potential sourceand the generator. v

6. A poly'phase induction motor having an external secondary resistance,a controller for adjusting the resistance, a pilot motor operativelyconnected to the controller, a generator operatively connected to theinduction motor, a constant-potential source of energy connected totheterminals of the generator and normally neutralizing the generatedpotential, said pilot motor'being interposed between theconstant-potential source and the generator and adapted to so adjust thecontroller as to keep the speed of the induction motor substantiallyconstant under varying loads.

In testimony whereof, I have hereunto subscribed my name this 28th dayof June, 1912.

HARVE R. STUART.

Vitnesses:

CLYDE C. MINER, FLORENCE 1. lanes.

